import java.util.Scanner;

public class Program5 {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        System.out.print("请输入你的学习成绩：");
        int score = console.nextInt();
//        if (score >= 90){
//            System.out.println("Grade A");
//        } else if (score >= 60 ^ score <90) {
//            System.out.println("Grade B");
//        } else {
//            System.out.println("Grade C");
//        }
        System.out.println(score >= 90? "A":score >=60? "B":"C");
    }
}